Fluid end access cover locking mechanism

ABSTRACT

A reciprocating fluid end access port plug includes an access plug body, expansion assembly and bolt. The access plug body can be shaped and sized to be received within the fluid end access port to inhibit a flow of fluid therethrough, and can define an inner end surface, an outer end surface defining an axially aligned threaded aperture, and a generally cylindrical wall extending therebetween. The expansion assembly can be configured to securely retain the access plug body in a desired plug position within the fluid end access port, and can include a locking drive member defining an aperture generally aligned with the threaded aperture of the access plug body, and a plurality of radially positioned locking segments. The bolt can have a threaded shaft configured to traverse through the aperture of the expansion assembly for threaded contact with the threaded aperture of the access plug body.

RELATED APPLICATION INFORMATION

This application claims the benefit of U.S. Provisional Application No. 62/635,300, filed Feb. 26, 2018, the contents of which are fully incorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to positive displacement fluid end plugs, and, in particular, to positive displacement fluid end plugs fixed by threaded rotation.

BACKGROUND

Oil and gas is commonly extracted from subsurface rock formations of the earth using a process called hydraulic fracturing, a technique that increases rock permeability by opening channels through which hydrocarbons can flow to recovery wells. In hydraulic fracturing, fluid is pumped into the rock formations at pressures that exceed the critical fracture pressure of the rock formations (sometimes as high as 50,000 PSI), where the high pressure fluid enters a reservoir rock and cracks or fractures it. Large quantities of solids or proppants are carried in suspension by the fluid into the fractures. When the pressure is released, the fractures partially close on the proppants, leaving channels for oil and gas to flow, thereby increasing well production.

Hydraulic fracturing therefore requires specialized pumping systems that can operate under very high pressures. One type of pump utilized to affect hydraulic fracturing is commonly referred to as a reciprocating positive displacement pump. Reciprocating positive displacement pumps typically have two main components: a power end and a fluid end (also known as the liquid or pressure side of the pump). The power end can have a motor and crank mechanism configured to convert rotational motion from the motor to reciprocating motion of a plurality of plungers positioned within the fluid end. The body of a fluid end is typically constructed of a single piece of material with internal flow passages. The plungers reciprocate axially within the fluid end to pressurize fracture fluids flowing within the internal flow passages. Suction valves and discharge valves control fluid into, and out of, the internal flow passages. In some cases, pressure differentials from the motion of the plunger can be utilized to open and close the valves.

As the fluid end is subjected to high pressurization and depressurization, which can occur up to three times per second as the pump reciprocates, the fluid ends are prone to cracking and failure due to metal fatigue. Friction, temperature, and exposure to corrosive elements can also take a toll on the material components. For ease in internal access and maintenance, fluid ends often include one or more access ports, which provide access to the internal flow passages, valves and plungers. When internal access is no longer needed, each access port is sealed with an access port plug.

Referring to FIG. 1, a fluid end 52 of the prior art is depicted. The fluid end 52 can include an internal flow passage 54 in fluid communication with a suction valve 56 and a discharge valve 58, configured to control a flow of fracture fluids during pressurization by the reciprocating plunger 60. As depicted, the fluid end 52 includes an access port 62 configured to enable access to the internal flow passage 54. The access port 62 can be selectively sealed by an access port plug 64. Conventional access port plugs 64 often include a two-part body, having an inner sealing pin 66 and an outer retaining nut 68 that serves to hold the inner sealing pin 66 in position when subjected to the high internal flow passage pressures during operation. Frequently, the internal diameter 70 of the access port 62 is helically threaded, such that the outer retaining nut 68 is configured to threadedly couple to the fluid end 52. To avoid failure while in service, generally the retaining nut 68 must be tightened down to a specific torque limit, which represents an added maintenance burden.

Over time the internal threads of the access ports can become worn (or even stripped) as they are continually subjected to stress during operation; particularly if they are frequently removed for internal inspection or maintenance. In some cases, the high pressures experienced during operation can cause the retaining nut 68 to seize within the fluid end 52, such that the access port plug 64 is unable to be removed without causing catastrophic damage to the fluid end 52. Premature failure of the access port threads and/or seizing between the threads and the access port plug typically marks the end of the serviceable life of the fluid end, as the fluid end cannot function without the access ports properly sealed. Replacement of the fluid end 52 is costly and results in maintenance down time.

The present disclosure addresses these concerns.

SUMMARY OF THE DISCLOSURE

Embodiments of the present disclosure provide a reciprocating pump fluid end access port plug configured to handle the excessive pressures and cyclical loading and unloading, without causing a breakdown of the internal threading of the access port, or otherwise shortening the serviceable life of the fluid end.

One embodiment of the present disclosure provides a reciprocating fluid end access port plug including an access plug body, an expansion assembly, and a bolt. The access plug body can generally be shaped and sized to be received within an access port of a fluid end to inhibit a flow of fluid therethrough. The access plug body can define an inner end surface, an outer end surface, and a generally cylindrical wall extending therebetween. The outer end surface can define an axially aligned threaded aperture. The expansion assembly can be configured to securely retain the access plug body in a desired plug position within the access port. The expansion assembly can include a locking drive member defining an aperture generally aligned with the threaded aperture of the access plug body, and a plurality of radially positioned locking segments. The bolt can have a threaded shaft configured to traverse through the aperture of the expansion assembly for threaded contact with the threaded aperature of the access plug body, wherein selective rotation of the bolt relative to the access plug body is configured to increase a threaded connection between the access plug body and the threaded shaft, thereby shifting the locking drive member of the expansion assembly axially relative to the plurality of locking segments and driving the plurality of locking segments radially outward from the locking drive member into contact with an inner radius of the access port.

In one embodiment, the access plug body can be constructed of a metallic material such as steel. In one embodiment, the threaded aperture of the access plug body can extend to a depth substantially between the outer end surface and the inner end surface. In one embodiment, the inner end surface of the access plug body can define a recess configured to receive a portion of a plunger of a reciprocating pump, when the plunger is moved to its point of maximum compression during reciprocation.

In one embodiment, the cylindrical wall of the access plug body can include one or more circumferential steps defining an axial contour of the cylindrical wall. In one embodiment, the axial contour of the cylindrical wall is defined by five circumferential steps, wherein the diameter of the first circumferential step is shared by the inner end surface, the diameter of the fifth circumferential step is shared by the outer end surface, and the second, third and fourth circumferential steps are respectively positioned between the first circumferential step and the fifth circumferential step. In one embodiment, the diameter of the second circumferential step is smaller than the diameter of the first circumferential step. In one embodiment, the diameter of the third circumferential step is smaller than the diameter of the second circumferential step. In one embodiment, the diameter of the four circumferential step is larger than the diameter of the first circumferential step. In one embodiment, the diameter of the fifth circumferential step is larger than the diameter of the fourth circumferential step. In one embodiment, the fifth circumferential step defines a flange configured to make abutting contact with a stepped inner diameter of the access port, thereby retaining the access plug body in a desired plug position to inhibit a flow of fluid through the access port and/or to inhibit traversal of the access plug body entirely through the access port.

In one embodiment, an exterior wall of the locking drive member generally defines a frustoconical shape configured to serve as a wedge to force the plurality of locking segments radially outward as the locking member is shifted axially. In one embodiment, the locking drive member further includes a tapered nose configured to ease in assembly of the locking drive member with the plurality of locking segments. In one embodiment, the bolt includes a head having an outer surface configured to engage with a driving tool and a flat inner surface configured to contact an outer face of the locking drive member to shift the locking drive member of the expansion assembly axially relative to the plurality of locking segments.

In one embodiment, the expansion assembly includes at least three locking segments. In one embodiment, each of the plurality of locking segments of the expansion assembly is substantially equal in shape and size. In one embodiment, each of the plurality of locking segments include an inner surface shaped and sized to conform to an outer diameter of the locking drive member, and an outer surface shaped and sized to conform to an inner diameter of the access port when the access port plug is in the desired plug position within the access port.

In one embodiment, the outer surface of the plurality of locking segments define a taper configured to impart an axial force component upon an inner diameter of the access port to aid in the retention of the access port plug in the desired plug position within the access port. In one embodiment, the outer surface of the plurality of locking segments define a grooved locking geometric configuration shaped and sized to mate with a corresponding geometric configuration defined by the diameter of the access port to aid in the retention of the access plug body in the desired plug position within the access port. In one embodiment, the outer surface of the plurality of locking segments define a concave locking geometric configuration shaped and sized to mate with a corresponding geometric configuration defined by the diameter of the access port aid in the retention of the access plug body in the desired plug position within the access port.

In one embodiment, each of the plurality of locking segments define a tab configured to reside within a corresponding channel defined within the outer end surface of the access plug body, thereby coupling each of the plurality of locking segments to the access plug body to inhibit axial movement of the plurality of locking segments relative to the access plug body, while enabling radial expansion of the plurality of locking segments relative to the access plug body.

Another embodiment of the present disclosure provides an access port plug including an access plug body, an expansion assembly, and a bolt. The access plug body can be configured to be received within an access port of a fluid end of a reciprocating pump to inhibit a flow of fluid through the access port. The access plug body can define an inner end surface, an outer end surface, and a generally cylindrical wall including one or more circumferential steps defining an axial contour of the cylindrical wall extending therebetween, the outer end surface defining an axially aligned threaded aperture. The expansion assembly can be configured to securely retain the access plug body in a desired plug position within the access port. The expansion assembly can include a locking drive member defining an aperture generally aligned with the threaded aperture of the access plug body, and a plurality of radially positioned locking segments, wherein each of the plurality of locking segments define a tab configured to reside within a corresponding channel defined within the outer end surface of the access plug body, thereby coupling each of the plurality of locking segments to the access plug body to inhibit axial movement of the plurality of locking segments relative to the access plug body. The bolt can have a threaded shaft configured to traverse through the aperture of the expansion assembly for threaded contact with the threaded aperture of the access plug body, wherein selective rotation of the bolt relative to the access plug body is configured to increase a threaded connection between the access plug body and the threaded shaft, thereby shifting the locking drive member of the expansion assembly axially relative to the plurality of locking segments to cause an expansion of the plurality of locking segments radially outward from the locking drive member and into contact with an inner radius of the access port.

Another embodiment of the present disclosure provides a method of plugging a fluid end access port of a reciprocating pump, comprising the steps of: positioning and access port plug within the fluid end access port, the access port plug including an access plug body, an expansion assembly, and a bolt, wherein the expansion assembly includes a locking drive member and a plurality of radially positioned locking segments; rotating the bolt relative to the expansion assembly, thereby increasing a threaded connection between the access plug body and a threaded shaft of the bolt, thereby shifting the locking drive member of the expansion assembly axially relative to the plurality of locking segments and driving the plurality of locking segments radially outward from the locking drive member to engage in contact with an inner radius of the access port, thereby securely retaining the access plug body in a desired plug position within the access port.

The summary above is not intended to describe each illustrated embodiment or every implementation of the present disclosure. The figures and the detailed description that follow more particularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be more completely understood in consideration of the following detailed description of various embodiments of the disclosure, in connection with the accompanying drawings, in which:

FIG. 1 is a cross section view of a fluid end and access port plug of the prior art.

FIG. 2 is an isometric view depicting an access port plug, in accordance with an embodiment of the disclosure.

FIG. 3 is an exploded view depicting the access port plug of FIG. 2.

FIG. 4 is a cross sectional view depicting the access port plug of FIG. 2.

FIG. 5 is an isometric view depicting a fluid end and a plurality of access port plugs, in accordance with an embodiment of the disclosure.

FIG. 6A is a cross section view depicting an access port plug inserted into the access port of a fluid end, in accordance with an embodiment of the disclosure.

FIG. 6B is a close up view depicting the access port plug of FIG. 6A.

FIG. 7 is a cross section view depicting an access port plug being inserted into a fluid end, in accordance with an embodiment of the disclosure.

FIG. 8 is a cross sectional view depicting an access port plug, in accordance with a second embodiment of the disclosure.

FIG. 9 is an exploded, perspective, cross sectional view depicting a cover plug being inserted into a fluid end, in accordance with the second embodiment of the disclosure.

FIG. 10 is a cross sectional view depicting an access port plug, in accordance with a third embodiment of the disclosure.

FIG. 11 is a partially exploded, perspective view depicting a cover plug being inserted into a fluid end, in accordance with the third embodiment of the disclosure.

While embodiments of the disclosure are amenable to various modifications and alternative forms, specifics thereof shown by way of example in the drawings will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims.

DETAILED DESCRIPTION

Referring to FIGS. 2-4, an access port plug 100 is depicted in accordance with an embodiment of the disclosure. The access port plug 100 can include an access plug body 102, an expansion assembly 104, and a bolt 106.

As best depicted in FIG. 4, the access plug body 102 can generally be cylindrically shaped, so as to be received within an access port of a fluid end to inhibit a flow of fluid therethrough. The access plug 102 can define an inner end surface 108, and outer end surface 110, and a generally cylindrical wall 112 extending therebetween. In one embodiment, the access plug body 102 can be constructed of a metallic material, such as steel. The outer end surface 110 can define an axially aligned threaded aperture 114, which can extend to a depth substantially between the outer end surface 110 and the inner end surface 108. In one embodiment, the inner end surface 108 can define a recess 116 configured to receive a portion of a plunger of a reciprocating pump, when the plunger is moved to its point of maximum compression during reciprocation.

In one embodiment, the cylindrical wall 112 of the access plug body 102 can include one or more circumferential steps 118A-E defining an axial contour of the cylindrical wall 112. In one embodiment, a diameter of a first circumferential step 118A can be shared by the inner end surface 108, and a diameter of a fifth circumferential step 118E can be shared by the outer end surface 110, such that a second circumferential step 118B, third circumferential step 118C and fourth circumferential step 118D are respectively positioned between the first circumferential step 118A and the fifth circumferential step 118E. In one embodiment, a diameter of the second circumferential step 118B can be smaller than the diameter of the first circumferential step 118A. In one embodiment, a diameter of the third circumferential step 118C can be smaller than the diameter of the second circumferential step 118B. In one embodiment, a diameter of the fourth circumferential step 118D can be larger than the diameter of the first circumferential step 118A, second circumferential step 118B, or third circumferential step 118C. In one embodiment, the diameter of the fifth circumferential step 118E can be larger than the diameter of the fourth circumferential step 118D. In one embodiment, the fifth circumferential step 118E can define a flange 120 configured to make abutting contact with a stepped inner diameter of the access port, thereby retaining the access plug body in a desired plug position to inhibit a flow of fluid through the access port, and to inhibit traversal of the access plug body 102 entirely through the access port. A rubber resilient seal may be placed in the groove created by step 118C, thereby enabling the access plug to better seal to an inner diameter of the access port

In one embodiment, the outer end surface 110 of the access plug body 102 can define one or more channels 122A-C configured to engage with one or more portions of the expansion assembly 104. As best depicted in FIG. 3, the expansion assembly 104 can be configured to securely retain the access plug body 102 in a desired plug position within the access port. The expansion assembly 104 can include a locking drive member 124 and a plurality of locking segments 126A-C. The locking drive member 124 can define an aperture 128 generally aligned with the threaded aperture 114 of the access plug body 102. In one embodiment, an exterior wall 130 of the locking drive member 124 can generally have a frustoconical shape configured to serve as a wedge to force the plurality of locking segments 126A-C radially outward as the locking drive member 124 is shifted axially. In one embodiment, the locking drive member 124 can further include a tapered nose 132 opposite to an outer face 134. The tapered nose 132 can be configured to ease in assembly of the locking drive member 124 with the plurality of locking segments 126A-C upon insertion of the access port plug 100 into an access port of a fluid end.

In one embodiment, the expansion assembly 104 can include at least a first locking segment 126A, a second locking segment 126B, and a third locking segment 126; although, the use of a greater or fewer number of locking segments is also contemplated. In some embodiments, each of the locking segments 126 can be substantially equal in shape and size. In other embodiments, some of the locking segments 126 can be proportionately larger than other locking segments 126.

With additional reference to FIG. 4, each of the plurality of locking segments 126 can include an inner surface 136 shaped and sized to conform to an outer diameter 138 of the locking drive member 124, and an outer surface 140 shaped and sized to conform to an inner diameter of the access port, when the access plug body 102 is in the desired plug position within the access port. In one embodiment, each of the plurality of locking segments can define a tab 150 (as depicted in FIG. 3) configured to reside within a corresponding channel 122A-C defined within the outer end surface 110 of the access plug body 102, thereby coupling each of the plurality of locking segments 126 to the access plug body 102 to inhibit axial movement of the plurality of locking segments 126 relative to the access plug body 102, while enabling radial expansion of the plurality of locking segments 126 relative to the access plug body 102.

With continued reference to FIGS. 2-4, the bolt 106 can have a threaded shaft 142 and a head 144. The threaded shaft 142 can be shaped and sized to traverse through the aperture 128 of the expansion assembly to make a threaded connection with the threaded aperture 114 of the access plug body 102. In one embodiment, the head 144 of the bolt 106 can have an outer surface 146 configured to engage with a driving tool, and a flat inner surface 148 configured to contact the outer face 134 of the locking drive member 124 to shift the locking drive member 124 of the expansion assembly 104 axially relative to the plurality of locking segments 126A-C. Selective rotation of the bolt 106 relative to the access plug body 102 can be configured to increase a threaded connection between the access plug body 102 and the threaded shaft 142, thereby shifting the locking drive member 124 of the expansion assembly 104 axially relative to the plurality of locking segments 126A-C, and expanding the plurality of locking segments radially outward from the locking drive member 124 into contact with an inner diameter of the access port.

Referring to FIG. 5, a fluid end 200 defining a plurality of access ports 202A-E is depicted in accordance with an embodiment of the disclosure. A corresponding plurality of access port plugs 100A-D are positioned within the access ports 202A-D in desired plug positions, so as to effectively inhibit a flow of fluid through the access ports 202A-D. A fifth access port plug 100E is shown in proximity to open access port 202E. FIGS. 6A and 6B depict an access port plug 100 positioned within the access port 202 of a fluid end 200 in a desired plug position. FIG. 7 depicts a partially disassembled access port plug 100 inserted partway within the access port 202 of a fluid end 200.

In operation, the access port plug 100 can be positioned within the access port 202 of a fluid end 200; the positioning of the access port plug 100 need not be made with a high degree of precision upon initial positioning. Thereafter, rotating the bolt 106 relative to the expansion assembly 104 can increase a threaded connection between the access port body 102 and the threaded shaft 142 of the bolt 106, thereby shifting the locking drive member 124 of the expansion assembly axially relative to the plurality of locking segments 126, and driving the plurality of locking segments 126 radially outward from the locking drive member 124 and to engage in contact with an inner diameter 204 of the access port 202, thereby shifting the access plug body 102 into a desired plug position within the access port 202, and retaining the access plug body 102 in said desired plug position thereafter.

With continued reference to FIGS. 2-7, in some embodiments, the outer surface 140 of the plurality of locking segments 126 can define a taper 152 (as best depicted in FIG. 6B) configured to impart an axial force component upon an inner diameter 204 of the access port 202 to aid in the retention of the access plug body 102 in the desired plug position within the access port 202.

With reference to FIGS. 8 and 9, in an alternative embodiment, the outer surface 140 of the plurality of locking segments 126 can define a grooved locking geometric configuration 154, shaped and sized to mate with a corresponding geometric configuration defined by the inner diameter 204 of the access port 202, to aid in the retention of the access port plug 102 in the desired plug position within the access port 202. For example, as depicted in FIGS. 8 and 9, the grooved locking geometric configuration 154 can include a plurality ridges 156A-C having a shallow taper 158 on an inner face 160 and a steep taper 162 on an outer face 164. A corresponding plurality of grooves 166A-B, for example defined by the steep taper 162 of a first ridge 156A and the shallow taper 158 of a second ridge 156B, can be defined between the plurality of ridges 156. The inner diameter 204 of the access port 202 can define a substantial mirror image of the grooved locking geometric configuration 154 defined by the outer surface 140 of the plurality of locking segments, thereby enabling selective locking engagement between the expansion assembly 104 and the access port 202. Alternative grooved locking geometric configurations 154 are also contemplated.

With reference to FIGS. 10-11, in yet another alternative embodiment, the outer surface 140 of the plurality of locking segments 126 can define a concave locking geometric configuration 168, shaped and sized to mate with a corresponding geometric configuration defined by the inner diameter 204 of the access port 202, to aid in the retention of the access port plug 102 and the desired plug position within the access port 202. In this embodiment, the concave locking geometric configuration 168 can be configured to aid in the axial positioning of the access plug body 102 in the desired plug position within the access port 202 of the fluid end 200. With the plurality of locking segments 126 expanded radially outward from the locking drive member 124 into engagement with the inner diameter 204, the concave locking geometric configuration 168 can inhibit axial movement of the expansion assembly 104 relative to the fluid end 200.

It should be understood that the individual steps used in the methods of the present teachings may be performed in any order and/or simultaneously, as long as the teaching remains operable. Furthermore, it should be understood that the apparatus and methods of the present teachings can include any number, or all, of the described embodiments, as long as the teaching remains operable.

Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions.

Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted.

Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended. 

What is claimed is:
 1. A reciprocating pump fluid end access port plug, comprising: a generally cylindrically shaped access plug body shaped and sized to be received within an access port of a fluid end to inhibit a flow of fluid therethrough, the access plug body defining an inner end surface, an outer end surface, and a generally cylindrical wall extending therebetween, the outer end surface defining an axially aligned threaded aperture; an expansion assembly configured to securely retain the access plug body in a desired plug position within the access port, the expansion assembly including a locking drive member defining an aperture generally aligned with the threaded aperture of the access plug body, and a plurality of radially positioned locking segments; and a bolt having an threaded shaft configured to traverse through the aperture of the expansion assembly for threaded contact with the threaded aperture of the access plug body, wherein selective rotation of the bolt relative to the access plug body is configured to increase a threaded connection between the access plug body and threaded shaft, thereby shifting the locking drive member of the expansion assembly axially relative to the plurality of locking segments and driving the plurality of locking segments radially outward from the locking drive member into contact with an inner radius of the access port.
 2. The access port plug of claim 1, wherein the access plug body is constructed of a metallic material.
 3. The access port plug of claim 1, wherein the inner end surface of the access plug body defines a recess configured to receive a portion of a plunger of a reciprocating pump.
 4. The access port plug of claim 1, wherein the cylindrical wall of the access plug body includes one or more circumferential steps defining an axial contour of the cylindrical wall.
 5. The access port plug of claim 1, wherein the axial contour of the cylindrical wall is defined by five circumferential steps, wherein the diameter of a first circumferential step is shared by the inner end surface, a diameter of the fifth circumferential step is shared by the outer end surface, and a second, a third and a fourth circumferential step are respectively positioned between the first circumferential step and the fifth circumferential step.
 6. The access port plug of claim 5, wherein the diameter of the second circumferential step is smaller than the diameter of the first circumferential step.
 7. The access port plug of claim 5, wherein the diameter of the third circumferential step is smaller than the diameter of the second circumferential step.
 8. The access port plug of claim 5, wherein the diameter of the fourth circumferential step is larger than the diameter of the first circumferential step.
 9. The access port plug of claim 5, wherein the fifth circumferential step defines a flange configured to make abutting contact with a stepped inner diameter of the access port, thereby retaining the access plug body in a desired plug position to inhibit a flow of fluid through the access port and/or to inhibit traversal of the access plug body entirely through the access port.
 10. The access port plug of claim 1, wherein an exterior wall of the locking drive member generally has a frustoconical shape configured to serve as a wedge to force the plurality of locking segments radially outward as the locking drive member is shifted axially.
 11. The access port plug of claim 1, wherein the locking drive member further includes a tapered nose configured to guide the locking drive member into assembly with the plurality of locking segments.
 12. The access port plug of claim 1, wherein the bolt includes a head having an outer surface configured to engage with a driving tool and a flat inner surface configured to contact an outer face of the locking drive member to shift the locking drive member of the expansion assembly axially relative to the plurality of locking segments.
 13. The access port plug of claim 1, wherein the expansion assembly includes at least three locking segments.
 14. The access port plug of claim 1, wherein each of the plurality of locking segments include an inner surface shaped and sized to conform to an outer diameter of the locking drive member, and an outer surface shaped and sized to conform to an inner diameter of the access port when the access port plug is in the desired plug position within the access port.
 15. The access port plug of claim 1, wherein the outer surface of the plurality of locking segments define a taper configured to impart an axial force component upon an inner diameter of the access port to aid in the retention of the access plug body in the desired plug position within the access port.
 16. The access port plug of claim 1, wherein the outer surface of the plurality of locking segments, define a grooved locking geometric configuration shaped and sized to mate with a corresponding geometric configuration defined by the diameter of the access port to aid in the retention of the access port plug in the desired plug position within the access port.
 17. The access port plug of claim 1, wherein the outer surface of the plurality of locking segments define a concave locking geometric configuration shaped and sized to mate with a corresponding geometric configuration defined by the diameter of the access port to aid in the retention of the access port plug in the desired plug position within the access port.
 18. The access port plug of claim 1, wherein each of the plurality of locking segments define a tab configured to reside within a corresponding channel defined within the outer end surface of the access plug body, thereby coupling each of the plurality of locking segments to the access plug body to inhibit axial movement of the plurality of locking segments relative to the access plug body, while enabling radial expansion of the plurality of locking segments relative to the access plug body.
 19. An access port plug, comprising: an access plug body configured to be received within an access port of a fluid end of a reciprocating pump to inhibit a flow of fluid through the access port, the access plug body defining an inner end surface, an outer end surface, and a generally cylindrical wall including one or more circumferential steps defining an axial contour of the cylindrical wall extending therebetween, the outer end surface defining an axially aligned threaded aperture; an expansion assembly configured to securely retain the access plug body in a desired plug position within the access port, the expansion assembly including a locking drive member defining an aperture generally aligned with the threaded aperture of the access plug body, and a plurality of radially positioned locking segments, wherein each of the plurality of locking segments define a tab configured to reside within a corresponding channel defined within the outer end surface of the access plug body, thereby coupling each of the plurality of locking segments to the access plug body to inhibit axial movement of the plurality of locking segments relative to the access plug body; and a bolt having an threaded shaft configured to traverse through the aperture of the expansion assembly for threaded contact with the threaded aperture of the access plug body, wherein selective rotation of the bolt relative to the access plug body is configured to increase a threaded connection between the access plug body and threaded shaft, thereby shifting the locking drive member of the expansion assembly axially relative to the plurality of locking segments to cause an expansion of the plurality of locking segments radially outward from the locking drive member and into contact with an inner radius of the access port.
 20. A method of plugging a fluid end access port of a reciprocating pump, the method comprising: positioning an access port plug within the fluid end access port, the access port plug including an access plug body, an expansion assembly, and a bolt, wherein the expansion assembly includes a locking drive member and a plurality of radially positioned locking segments; rotating the bolt relative to the expansion assembly, thereby increasing a threaded connection between the access plug body and a threaded shaft of the bolt, thereby shifting the locking drive member of the expansion assembly axially relative to the plurality of locking segments and driving the plurality of locking segments radially outward from the locking drive member into engaging contact with an inner radius of the access port, thereby securely retaining the access plug body in a desired plug position within the access port. 